Hydraulic draft gears



Oct. 20, 1959 Filed June 6, 1956 1'. o. HENRIKSON HYDRAULIC DRAFT GEARS5 Sheets-Sheet vl//l 22 la 62- `l6 `R/l//fl/J//////////7/////}///////INVENT OR Thor' O. Henriksen A'ITORNEY 20, 1959 T. o. HENRIKSONHYDRAULIC om GEARS Filed June 6, 1956 5 shans-sheet 3,

INVENTOR Thon 0. Henriksen 4 A'ITORNEY Oct-20, 1 T.. o. HENRKsoN'2,909,292

' v HYDRAULIC DRAFT GEARS Filed June 6, 1956 v 5 Sheets-Sh eet 4 NVENTOR77 20!" O. Henri/(son A'ITORNEY United States PatentOfiiice 2309392Patented Oct. 20, 1959 HYDRAULIC DRAFT VGEARS Thor 0. Henriksen,Seattle, Wasl., assignor to PacificCar and Foundry Company, Renton Wash.

Application June 6, 1956, Serial No. 589 584 7 Claims. (Cl.213-43)rected to a shoek-absorber of the type in which Shock loads are absorbedin part by throttling of hydraulic fluid under pressure throughpassageways, and in part by compression of a spring axially disposed ina cylinder so as to oppose axial sliding of a piston.

It is the general object of this invention to 'provide an improved draftgear of this type combining maximum ability to absorb Shock loads 'withincreased rapidity of return of the parts to a normal position afterremoval of an applied load; and to provide an improved Construction andcombination of parts affording improved performance with greaterprotection against accidental in- J 'Y- e In a shock-absorber of thistype, fluid throttled through passageways formed in the piston passesinto a chamber formed by that portion ofthe cylinder bore lying behindthe piston. This rear chamber also recei ves a piston-red axially. Sincea portion of the rear chamber is occupied by the piston-rod, its Volumeincreases in' proportion to the movement of the piston andthe differencein crosssectional area of the bore and the piston-rod;'while the IVolume of the chamber in the cylinder lying ahead of the pistondecreases in proportion to the entire cross-sectional area of the boreand the movement of the piston. The difference in change of Volumebetween the two chambers may be accommodated by provision of suitablereservoirs for receiving the surplus fluid. Such reservoirs havepreviously been provided in the form of a free piston cooperating with acylinder containing pressurized gas, such that the surplus fluid wasaccommoclated by a movement of the free piston further compressing theconfined gas, as in the patent to Welch, No. 880,257. A' reservoir ofthis :type is shown in the Welch patent, formed within the piston of adraft gear with a fluid entry port formed in the piston face confrontingthe compressed fluid lying ahead 'of the piston. In order to permitrapid return flow of` :the fluid contained in the reservoir upon removalof' a load from the piston-rod, and consequent rapid return of thepiston to an unloaded position, the fluid entry port has been made of asufficiently large diameter in proportion to the piston diameter as toprevent the application of a throttling effect to fluid entering thereservoir which would materially impede the piston stroke, andthrottling has been primarily confined to the passageways extendingthrough the piston and joining the two fluid chambers formed by thecylinder and the piston.

It is an object of this invention to provide restricted oriice means for-throttling fluid entering an expansible excess-fluid reservoir in ahydraulic draft gear during a shock-absorbing stroke of the piston,combined 'with valved port means to permit rapid escape of the fluidfrom the reservoir upon release of the load from the draft gear, and aconsequently rapid return strke of the piston to it's original position.

Throttling passageways previously provided in draft gears of this type,extending through the 'piston and connecting the cylinder chambersseparated by the piston, have been made of such a small diameter inproportion to the piston diameter as to secure a substantial throttlingefiect, and have not permitted rapid return flow of the fluid during thereturn stroke because of this relatively ;small size and concomitantthrottlng elfect. Consequently, the return stroke, as well as theshock-absorbng stroke, has been impeded by throttling of the fluidthrough these passages.

It is a further object of this invention to provide return-flow ports inthe piston of a hydraulic draft gear of this type, of such a largediameter relative to the piston diameter as to produce little throttlingeflect and a rapid return flow during the return stroke, together withoneway valve means for the return-flow ports, and relatively smallthrottle passageways producing a more greatly throttled and consequentlyslower flow during the shockabsorbing stroke than during the returnstroke.

Draft gears of the present type have been provided with a main hydraulicfluid reservoir comprising a double- Walled chamber partiallysurrounding the working cylinder circumferentially, and connected byports with the cylinder'chamber, as in the patent to Cotton No.1,614,657. A screw-capped filler hole may be provided in the externalwall of this reservoir for the purpose of filling the fluid chambers ofthe draft gear. This filler hole is generally so placed in the outerWall as to prevent complete filling of the reservoir, so that some ofthe surplus fluid passing into the rear chamber of the cylinder may beaccommodated therein, and so that excessive pressures occurring throughmechanical failures or other accidental factors will not producedestructive stresses on the walls of the main reservoir, but will beabsorbed by compression of the air entrapped in the main reservoir.However, human error may nevertheless result in complete filling of them-ain reservoir with hydraulic fluid, with consequent danger ofdestructive pressures occurring.

It is accordingly a further object of this invention to providecompressible means for absorption of excessive fluid pressuresaccidentally occurring within the main reservoir of a draft gear. Thesemeans comprise compressible pads of cellular solid material with afluid-impervious surface covering, placed within the main reservoir toabsorb excess fluid pressure caused by overfilling or other accidentalfactors.

V i It is a still further object of this invention to provide animproved mounting means in combination with a draft gear of this type,having improved resistance to cocking and galling of the piston withinthe cylinder under the influence of Shock loads applied in a non-axialor skew 'direction by a coupler associated with the draft gear.

Referring to the drawings:

Fig. 1 is a longitudinal section of a recommended em- -bodirnent of thepresent invention, with parts shown in normalor no-load position, ta'kenalong line 1-1 of Fig. 6;

Fig. 2 is a similar longitudinal section of the same device, with partsshown in their relative positions when the device is subjected to aload;

Fig. 3 is an enlarged view of a partial section of the same device, withparts shown in their relative positions during a` return stroke from theposition of Fig. 2 to that of Fig. 1;

Fig. 4 is a partial sectional cutaway view of the piston member takenalong line 6-6 of Fig. 1;

Fig. 5 is an axial section taken along line 5-5 .of Fg. 3;

Fig. 6 is an axial section taken along line 6-6 of Fig. 1;

Fig. 7 is a schematic plan view of a first mounting means for the draftgear, constructed according to this invention, With parts shown innormal or no-load position;

Fig. 8 is a schematic elevation of the mounting means of Fig. 7;

Fig. 9 is a schematic elevation similar to Fig. 8, with parts shown inloaded position;

Fig. 10 is a schematic plan view of an alternative improved mountingmeans for the draft gear, with parts shown in normal or no-loadposition;

Fig. ll is a schematie elevation of the mounting means of Fig. 10; and

Fig. 12 is a schematic elevation similar to Fig. ll, with parts shown inloaded position.

In Fig. l, piston 10 having annular flange 12 is placed in axiallyslidable relationship within bore 13 of cylinder 11, and is adapted tobe driven by a shock-load in the direction shown by arrow L of Fig. 2,against the resilient bias of compression spring 14 axially disposedwithin forward chamber 15 of cylinder 11.

A pair of main fluid reservoirs 23, 24 are formed about cylinder 11 bymeans of channel members 25, 26, welded to cylinder 11 as at 27.Threaded filler holes formed in walls 25, 26 and bosses 33 are placedintermediate the extremities of the reservoirs 23, 24 to permit onlypartial filling of the draft gear with hydraulic fluid, and are providedwith threaded caps 34,

To furnish means for absorption of excess fluid pressures which mayaccidentally occur in the reservoirs 23, 24 through overfilling or otherfactors, pads 35 of cellular material, preferably neoprene foam, areplaced therein. Covers 36 of a suitable fluid-impervious material areplaced over pads 35 and secured to walls 25, 26 by means of screws 37and gasket 38 to prevent saturation of pads 35 with hydraulic fluid. Inthe event that excess pressure should develop, pads 35 will becompressed sufliciently to prevent disruptive stresses in reservoirs 23,24.

An annular cap 40 is placed within the open end of cylinder 11 and aboutpiston 10, enclosing a rear chamber 42 and rendering it fluid-tight. Cap40 is provided with annular grooves 42, 44 and annular seals 43, 45cooperating with the surfaces of cylinder 11 and piston 10 influid-scaling relationship. Cap 40 is secured in place by means ofthreaded ring 47 engaging threads 48 formed in cylinder 11 and bearingagainst flange 46 of cap 40, which abuts on shoulder 41 formed incylinder 11.

A collapsible bellows seal 49 is placed over cap 40 to prevent the entryof dirt and dust into the draft gear. Bellows seal 49 is secured topiston 10 by means of clamping ring 50, and to ring 47 by means ofgasket ring 51 and screws 52 assembled in tapped holes formed in ring47. An annular oil seal 53, 54 may be placed about piston 10 and axiallysecured by means of annular plate 55, secured to ring 47 by means ofscrews 52, gasket ring 51, and bellows seal 49.

Cylinder 11 may be initially formed with an axial hole 57 at its closedend, for convenience in manufacture. Hole 57 is closed and sealed bymeans of plug 58, welded as at 59 to cylinder 11.

Flange 12 of piston 10 is provided with a series of circumferentiallyspaced longitudinally disposed tapered passageways 16 and may be furtherprovided with chamfer 17. A pair of longitudinally spaced annulargrooves 18, 19 and a group of circumferentially spaced longitudinallydisposed grooves 22 are formed in the walls of bore 13. Grooves 18 and22 cooperate with groove 16 to provide fluid passageways of combinedcross-sectional area. A pair of radial ports 28, 29, as shown in Fig. 6,are formed in cylinder 11 and provide communication between mainreservoirs 23, 24 and grooves 19.

Upon application of a shock load to piston 10, it moves in the directionof arrow L in Fig. 2. Fluid pressure in chamber 15 causes a throttlingflow through tapered passageways 16, and further flow through grooves 22into rear chamber 42, as shown 'by arrows in Fig. 2. This throttlingflow absorbs the shock load in conjunction with spring 14, and appliesit slowly and uniformly to cylinder 11. A portion of the throttled fluidflows from grooves 22 through groove 19 and ports 28, 29 into mainreservoirs 23, 24, compressing any air trapped therein. As piston 10moves toward the position of Fig. 2, and flange 12 slidably engages bore13, groove 18 is covered thereby, so that fluid is thereafter throttledthrough a minimum orice equal to the cross-sectional area of thatportion of tapered passageways 16 adjacent shoulder 62, formed by bore13 and groove 18. Tapered passageways 16 may be so formed that theireffective cross-sectional areas at any position of piston 10 render thepressure obtaining in chamber 15 constant at all positions; thus, theforce absorbed by cylinder 11 will remain substantially constantthroughout the stroke. A constant application of force minimzes the peakforce absorbed, and thus represents an ideal condition, as is well knownin the art.

In order to 'assist rapid return of piston 10 in the position of Fig. 1after the removal of a shock load, a series of return-flow ports 63 oflarge cross-sectional area relative to passageways 16 are formed inflange 12, connecting chambers 42 and 15, and are circumferentiallyinterspersed between grooves 16, as shown by Fig. 6. One-way valvemembers are placed in these ports to prevent unthrottled flowtherethrough during the shockabsorbing stroke, while permitting freeflow during the return stroke. These valves comprise balls 64,yieldingly urged into engagement with conical seats 65, formed aboutports 63, by means of compression springs 66. As best shown in Fig. 4, aseries of grooves 67 of circula r section are formed circumferentiallyabout ports 63, affording communication between ports 63 and chamber 15when balls 64 are displaced from seats 65. An annular plate 69 issecured to the forward face of flange 12 by means of screws 70, in orderto provide a seat for compression springs 66. U-shaped grooves 68 areformed in the forward face of flange 12 about the ends of ports 63, toprovide communication between ports 63 and chamber 15 behind plate 69.

As a shock load is applied to piston 10, tending to drive it in thedirection of arrow L in Fig. 2, balls 64 are forcibly seated uponconical seats 65 by the increased fluid pressure obtaining in chamber15. Thus, during the -shock-absorbing stroke, fluid flow from chamber 15is confined to throttling passageways 16 and the grooves connectedtherewith, and does not occur in ports 63.

Upon removal of the load from piston 10, potential energy stored incompressed spring 14 tends to return piston 10 in the direction of arrowR in Fig. 3. As the pressure obtaining in rear chamber 42 approaches andthen surpasses that obtaining in chamber 15, balls 64 are lifted fromseats 65 against the bias of spring 66, and a rapid return flow occursfrom chamber 42 through ports 63, grooves 67, and grooves 68 to chamber15, as shown by arrows in Fig. 3, as well as through grooves 22 and 28and throttling passageways 16.

As previously discussed, fluid displaced from chamber '15 during theshock-absorbing stroke of piston cannot be entirely accommodated bychamber 42, because the decrease in Volume of chamber 15 is proportionalto the cross-sectional area of bore 13, while the corresponding increasein Volume of chamber 42 is in proporton only to the difierence inoross-sectional areas of bore 13 and piston 10'. Only a small portion ofthe excess fluid displaced is accommodated within main reservoir 23, bycompression of air entrapped therein.

In order to accommodate the remaining excess fluid displaced, an annularaxial extension 72 having internal bore 73 is formed integrally withpiston 10, internally containing 'eit''aansible`&eXcess-fliid'feSeri/oir 74. A 'compressible accumulator bag 76,flexible and impervious to hydraulic fluid, is placed within bore 73 andfilled With gas to a predetermined pressure. Fluid received within'excess-fluid reservoir 74 is accommodated by compres- "sion ofaccumulator bag 76. Reservoir 74 is enclosed by means of Valve member75, received in axially sldable relationship within enlarged bore 77 atthe open end of bore 73. Valve member 75 bears upon an annular ring 78seated upon shoulder 79 formed'by the junetion of bores 73 and 77,and'is resiliently biased into engagement therewith by means ofcompression 'spring 80, for a purpose further to be described.compression spring 80 is retained within bore 77 by means of an annularring 84 and snap-ring 85, which cooper'ates with a suitable grooveformed in the wall of bore 77.

A throttling orifice 82 formed axially through v-alve member' 75,connectng expansible reservoir 74 with chamber 1 5. A series ofreturn-flow ports 83 are radially disposed in the walls of bore 77,-communicating with chamber 15, :and 'are normally closed by Valve member75 when in the position of Fig. 1.

During the shock-absorbng stroke a portion of fluid displaced fromchamber 15 is throttled through port 82 into expansible reservoir 74,with consequent absorption of force, as shown by arrows in Fig. 2.Accumulator bag 7'6 is compressed by the fluid entering reservoir 74until the pressu'e of the gas confined therein' is equal to the-pressure of the fluid. Valve member 75 remains seated upon ring 78during the -shock-absorbing stroke, under the bias of spring 80` and thepressure of fluid in chamber 15, and thus closes ports 83 and preventsany unthrottled flow therethrough.

Upon removal of the applied load from piston 10, it is driven in thedirection of arrow R in *Fig. 3' by compressed spring 14 and by thepressure of the fluid in chamber 74. A rapid return flow of fluid fromexpansible reservoir 74 to chamber 15'- is aided by the compressed gasconfined within accumulator bag 76. Ports 83 are exposed to exp-ansiblereservoir 74 during the return sti-oke by an axial movement of Valvemember 75 :away from ring 78, resulting when the relatively higher fluidpressure obtaining in reservoir 74 than in chamber 15 is suflicient toovercome the resilient bias of spring 80. Return flow from reservoir 74to chamber 15 takes place through ports 83 as well as through orifice82, as 'shown by arrows in Fig. 3. Ports 83` are sufliciently large innumber and cross-sectional area, as best seen in Fig. 5, to provide fora highly increased rate of flow relative to that obtainable throughorifice 82, and prevent any materially flow-rest raining amount ofthrottlng of the fluid passing into chamber 15 from reservoir 74. Valvemember 75, orifice 82, and ports 83, with their associated means, thusCooper-ate to provide a slower and more highly throttled flow fromchamber 15 to reservoir 74 during the shock-absorbing stroke than duringthe return stroke, which is characterized by a relatively rapid andunthrottled flow in the reverse direction with a consequent rapidity ofreturn of piston 10 to its unloaded position.

Improved mounting means for the draft gear of this invention 'are shownin Figs. 7, 8 and 9, and a modification representing a furtherimprovement is shown in Figs. 10, ll and 12. In Figs. 7 and 8, schematically showing the mounting means in plan and elevation views,respectively, the body of the draft gear comprisng cylinder 11 andchannel members 25 and 26 abuts members 92. Flanged members 92 areaiiixed to car structure beam members 90, 91, serving to transfer theload from the draft gear to the car structure. The internal members ofthe draft gear are shown schematically, including spring 14, piston 10,and flange 12 cooperating with cylinder 11 in axially sldablerelationship. Piston 10 contacts a rectangular follower plate 94. Aknuckle coupler 95, or other means'subj-ect to shock loading, contactsfol- `6 lower plate 94 and is adapted to transmit appled forces thereto,reg'ardless of direction.

'A pairof flanged members 96 are rigdly affixed to' beam members 90, 91and act as stops for follower plate 94, which abuts thereon -whencoupler is subjected to a load in tension, as shown by arrow T in Fig.8.

A yoke member 98contacts face 101 at the closed end of cylinder 11, andis provided with slot 99 cooperating with a key 97 aflixed to, andtransfixing, coupler 95. When coupler 95 is' subjected to a load intension, as shown by arrow T in Fig. 8, key 97 is drawn into abutmentwith the. forward end of slot 99. Force T is transmitt'ed by key 97through yoke 98, cylinder 11, piston 10, spring 14, follower 94, andflanged members 96 to beam members 90, 91 delivering a shock-absorbingaction to the car structure.

Application of a load in compression, as shown by arrow C in Fig. 9,drives coupler 95, follower plate 94, piston 10, flange 12, andcompression spring 14 to the right and produces a shock-absorbing actionof the draft gear,as previously described. Absorbed force is transmittedby cylinder 11 through flanged members 92 to beam members 90, 91.

An improvement in resistance to cooking of piston 10 and consequentgalling or scoring of cylinder 11 resides in the combination andarrangement of parts described in the present draft gear. Under theinfluence of a skew load, as represented by arrow S in Fig. 9, exertedin any direction other than axially of the draft gear, coupler 95 tendsto twist piston 10 and flange 12 in cylinder 11. Such skew loadscommonly occur in practice, as when the vehicles associated with coupler95 are upon a curved or an irregularly inclned track. The provision andlocation of follower plate 94, axially sldable between beam members 90,91 and in axially spaced relation with flange 12, provides improvedresistance to cockirg, because the moment arm acting to resist torsionis equal to the axial distance between the oppositely disposed faces offollower plate 94 and flange 12, rather than the relatively small axialthickness of flange 12 alone.

In the arrangement of Figs. 10, 11 and 12, the draft gear is reversedrelative to the vehicle undercarriage frame, achieving a still furtherimprovement in resistance to cocking of piston 10 and flange 12 incylinder 11. Follower plate 94 contacts flanged members 92, yoke 98, andpiston 10. Cylinder 11 and channel members 25, 26 are placed in axiallysldable relationship within beam members 90, 91, and abut flangedmembers 96 under the influence of a load in tension, as shown by arrow Tin Fig. ll. operation of the draft gear and mounting means under theinfluence of loads in tension or compression, as shown by arrows T' inFig. ll and arrow C' in Fig. 12, respectively, is the same as for thearrangements of Figs. 7 and 9, with the exception that cylinder 11 nowassumes the former functions of follower plate 94, and vice versa.

Upon application of a skew load, as represented by arrow S' in Fig. 12,exerted in any direction other than axially of the draft gear, coupler95 tends to twist cylinder 11 relative to piston 10 and flange 12. Theassociation of cylinder 11 in rigid assembly with coupler 95 results inapplication of the twisting moment through the walls of cylinder 11 tobeam members 90, 91, with which cylinder 11 is associated in axiallysldable relationship. Because the moment arm acting to resist torsion isnow equal .to the entire axial length of cylinder 11, which length maybe greater than the moment arm of the previous arrangement, a stillfurther improvement in resistance to cooking of cylinder 11 relative topiston 10 and flange 12 is obtainable.

What I claim is:

1. In a hydraulic draft gear comprising a piston and a cylinderassembled for relative axial movement, a piston rod projecting from thefront face of the piston through the cylinder wall and movable With thepiston within the cylinder, a spring in said cylinder abuttirg the inneropposite face of the piston and normally u'ging said piston towards thefront end of the cylinder, front and rear fluid confining chamber formedin said cylinder and separated by said piston, ports extending throughsaid piston and connecting said chambers, normally seated valve meansfor preventing flow of fluid through said ports upon movement of thepiston toward said front face under shock abso'bing strokes butpermitting free flow of fluid during return stroke, tapering throttlingpassages formed in the peripheral surface of said piston incommunication with the cylinder, grooves formed in the wall of saidcylinder communicating with said rear chamber and withsaid throttlingpassageways to permit fluid flow through said tapering throttlingpassageways and said groves to be varied by relative aXial movement ofthe piston and the cylinder, a recess formed within the inner face ofsaid piston 'to provide a fluid reservoir within the piston, apassageway forming an entrance to said reservoir, a valve normallyclosing said passageway during the power stroke of the piston regardlessof pressure, and an orifice opening into said fluid reservoir to allowthe flow of surplus fluid into said reservoir *in said piston inproportion to the displacement of said piston rod as the latter entersthe front cylinder upon the return stroke of said piston.

2. The structure of claim 1 characterized in that the fluid reservoirwithin the piston is formed in an annular extension projecting from therear face thereof.

3. The structure of claim 1 characterized in that the fluid reservoirwithin the piston is formed in an annular extension projecting from therear face thereof, said reservoir containing an accumulator bag forcompression upon entry of fluid under pressure into the reservoir.

4. The structure of claim 1 characterzed in that the valve normallyclosing said passageway during the power stroke of the piston regardlessof pressure is of cylndrical .form and is slidably as sociated withports formed in the lateral wall definng the reservoir within thepiston.

5. The structure of claim 1 characterized in 'that the valve normallyclosng said passageway during the'power stroke of the' piston regardlessof pressure -is spring seated and of cylindrical form and is slidablyassociated with ports formed in the lateral wall definng the reservoirwithin the piston.

6. The structure of claim 1 characterzed in that the orifices openinginto the fluid reservoir to allow the flow of surplus fluid intothe'reservoir in the piston s formed in the valve normally closing thepassageway during the power stroke. n r

7. The structure of claim 1 characterized in that a main reservoir isprovided exteriorly of the cylinder assembly and is in communicationwith the front fluid confining chamber formed in the cylinder, saidreservoir containing absorption pads for accommodating excess fluidpressures.

'References Cited in the file of this patent UNITED STATES PATENTS1,519,451 Harris Dec. 16, 1924 1,955,349 Stevens Apr. 17, 1934 2,20l,912'Morgan May 21, 1940 2,533,825 Lowry Dec. 12, 1950 2,590,406 Haas Mar.25, 1952 2,737,301 Thornhill Mar. 6, 1956 2,8l6,670 Edwards et al. Dec.17, 19'57 FOREIGN PATENTS 1,113,867 France Oct. 22, 1954

